a) Field of the Invention
The present invention relates to an optical head device which is used for recording into or reproduction from an optical record disk such as a CD or a DVD. More specifically, the present invention relates to a lens holder support mechanism which movably supports an objective lens in a tilt direction as well as a tracking direction and a focusing direction.
b) Description of the Related Art
In an optical head device which is used for recording into or reproduction from an optical record disk such as a CD or a DVD, a lens holder support mechanism with a wire suspension system has been known in which a lens holder provided with an objective lens is supported by wires such that the objective lens is capable of being driven in a tracking direction, a focusing direction and a tilt direction. The optical head device with the wire suspension system includes a lens holder which holds an objective lens, a lens holder support member which supports the lens holder with wires, and a magnetic drive mechanism for driving the lens holder in a tracking direction, a focusing direction and a tilt direction. The magnetic drive mechanism includes a focusing drive coil, a tracking drive coil, and a tilt drive coil provided on a side face of the lens holder and a tracking and focusing drive magnet and a focusing and tilt drive magnet provided on the lens holder support member.
As shown in FIG. 8, a lens holder 101 which holds an objective lens 100 is supported movably in the tracking direction “Tr”, the focusing direction “Fo” and the tilt direction “Ti” by six wires 102, 103, 104, 105, 106 and 107. Three pieces of six wires 102 through 107 respectively constitute a set of wires, and their base end sides are fixed on a lens holder support member and their front end sides are fixed on both sides of the lens holder 101 in the tracking direction. Two sets of wires 102, 103, 104 and 105, 106, 107 are respectively fixed on the lens holder 101 such that each set of three wires are fixed at an upper, a lower and a middle position in the focusing direction “Fo”. Required electric currents are respectively applied to a focusing drive coil, a tracking drive coil and a tilt drive coil through the wires 102, 103, 104 and 105, 106, 107. The wires 103 and 106 disposed between the upper and the lower wires 102, 104 and 105, 107 are used for applying an electric current to the tilt drive coil.
In the optical head device with the wire suspension system constructed such that the objective lens 100 is movable in the tilt direction “Ti”, six wires 102, 103, 104, 105, 106 and 107 fixed on both sides of the lens holder 101 are respectively made of the same material and the same diameter of wire (cross sectional area) as shown in FIG. 8. Two sets of wires 102, 103, 104 and 105, 106, 107 are respectively disposed with an equal interval in the focusing direction “Fo”.
According to the construction described above, the supply of energy to the tilt drive coil can be simplified. However, the wires 103 and 106 disposed at the middle position in the focusing direction “Fo” may provide an unnecessary thrust force to the lens holder 101 at the time of the movement of the objective lens 100. Therefore, when the lens holder 101 is subjected to a rolling motion by applying an electric current to the tilt drive coil to control in the tilt direction “Ti”, the objective lens 100 may occur a tilt movement which is not expected.